Bonding, antibonding and tunable optical forces in asymmetric membranes

作     者：Rodriguez, Alejandro W. McCauley, Alexander P. Hui, Pui-Chuen Woolf, David Iwase, Eiji Capasso, Federico Loncar, Marko Johnson, Steven G. 

作者机构：MIT Dept Math Cambridge MA 02139 USA Harvard Univ Sch Engn & Appl Sci Cambridge MA 02138 USA MIT Dept Phys Cambridge MA 02139 USA 

出 版 物：《OPTICS EXPRESS》 (Opt. Express)

年 卷 期：2011年第19卷第3期

页      面：2225-2241页

核心收录：

学科分类：070207[理学-光学] 07[理学] 08[工学] 0803[工学-光学工程] 0702[理学-物理学] 

基　　金：Army Research Office through the ISN [W911NF-07-D-0004] Defense Advanced Research Projects Agency (DARPA) [N66001-09-1-2070-DOD] 

主　　题：Computation methods Guided mode resonance Optical force Planar waveguides Resonant modes Waveguide modes 

摘      要：We demonstrate that tunable attractive (bonding) and repulsive (anti-bonding) forces can arise in highly asymmetric structures coupled to external radiation, a consequence of the bonding/anti-bonding level repulsion of guided-wave resonances that was first predicted in symmetric systems. Our focus is a geometry consisting of a photonic-crystal (holey) membrane suspended above an unpatterned layered substrate, supporting planar waveguide modes that can couple via the periodic modulation of the holey membrane. Asymmetric geometries have a clear advantage in ease of fabrication and experimental characterization compared to symmetric double-membrane structures. We show that the asymmetry can also lead to unusual behavior in the force magnitudes of a bonding/antibonding pair as the membrane separation changes, including nonmonotonic dependences on the separation. We propose a computational method that obtains the entire force spectrum via a single time-domain simulation, by Fourier-transforming the response to a short pulse and thereby obtaining the frequency-dependent stress tensor. We point out that by operating with two, instead of a single frequency, these evanescent forces can be exploited to tune the spring constant of the membrane without changing its equilibrium separation. (C) 2011 Optical Society of America